Earlier quoted context omitted.
California is at-will. And it still requires 60 days notice for a mass-layoff, thorough a separate act, because it's a special case that's covered by a separate law. > “an employer may not order a mass layoff, relocation, or termination at a covered establishment unless, 60 days before the order takes effect, the employer gives written notice of the order” https://www.dir.ca.gov/dlse/Cal-WARNAct.html
Without sounding dumb, this is saying that a company has to tell you 60 days ahead of time that in 60 days they will fire you? edit: Thank you for the clarification, appreciate the added insights.
Note, I don't benefit from this since I'm not in CA, but I still think it's a good idea.